Reacción a "Reactions to the results of the phase 3 malaria vaccine R21 trial"

Phase 3 clinical trials for vaccine registration, such as this one, are rigorously executed studies under external monitoring, and the design and performance is under scrutiny by WHO expert committees before recommending this R21 vaccine and by external reviewers from the Lancet. Thus, the study is generally of good quality, although with certain limitations that are mentioned in the discussion and discussed below. 

The study demonstrates the utility of a second malaria vaccine developed in Oxford, with a formulation very similar to the first vaccine that the WHO recommended after another larger multicentre phase 3 trial and a series of pilot implementation studies in three African countries (RTS,S/AS01E or GSK's Mosquirix). Both consist of a malaria parasite antigen based on the circumsporozoite protein from the surface of Plasmodium falciparum injected by the transmitting mosquito, fused to the hepatitis B virus surface antigen and formulated with an adjuvant that stimulates an inflammatory response by the innate immune system, and induces high levels of antibodies to the parasite. 

The vaccine shows high efficacy in areas of seasonal malaria when administered just before the rainy months associated with high transmission of infection, and less efficacy in sites of less intense and perennial transmission. The authors suggest that a large number of vaccine doses can be produced cost-effectively, which will benefit more African children, given the current manufacturing limitations of the other available vaccine. As with the covid-19 pandemic, the availability of more than one vaccine allows for greater coverage. Both vaccines are considered first-generation vaccines, with improving efficacy, and further research is needed to investigate knowledge gaps (e.g. why they do not protect 90-100% of children) in order to optimise them for second generations.  

The duration of efficacy of such a vaccine still needs to be monitored to further assess its public health impact, as well as its efficacy in areas of Africa where malaria transmission is high and year-round. The two East African sites included have very low malaria transmission at present and are not fully representative of the epidemiology that exists in much of the continent's endemic areas, where malaria is one of the leading causes of illness and mortality in the population.